Processing method of workpiece

Abstract

To provide a processing method of a workpiece capable of suppressing manufacturing cost on thinning a workpiece while maintaining processing quality.SOLUTION: A processing method of a workpiece includes: a preparation step 101 of preparing a support substrate having an open hole and a sheet including a thermoplastic resin; a fixing step 102 of thermally pressurizing and fixing the workpiece and the support substrate via the sheet by making a front face of the workpiece confront with a front face side of the sheet and making one face of the support substrate confront with a rear face side of the sheet, and heating the sheet; a processing step 103 of holding the support substrate to which the workpiece is fixed with a holding table and grinding a rear face of the workpiece; a support substrate peeling step 104 of peeling the support substrate from the sheet by supplying a fluid from the other face of the support substrate via the open hole for forming a gap between the support substrate and the sheet; and a sheet peeling step 105 of peeling the sheet from the workpiece.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for treating a workpiece. [Background technology]

[0002] In the manufacturing process of semiconductor devices, a step of thinning the semiconductor wafer by grinding its back surface is carried out at the semiconductor wafer stage before it is separated into individual devices in order to make the devices have a desired thickness.

[0003] In recent years, due to the miniaturization of equipment on which semiconductor devices are mounted, there is a demand for device chips to be as thin as possible. Since thinned semiconductor wafers are difficult to handle, a method is used in which the front side of the semiconductor wafer is attached to a support substrate before grinding, and the semiconductor wafer is peeled off from the support substrate after grinding.

[0004] Here, as a method for attaching the support substrate, a method is known in which a wax film is formed using wax that has been melted by heating to form a solid wax film, and the semiconductor wafer and the support substrate are fixed via this wax film.

[0005] However, with this method, depending on the skill level of the worker, the wax film thickness may become uneven, or air or particles may be trapped, resulting in depressions or undulations after polishing.

[0006] In addition, a cleaning process is required to remove the wax after grinding, and there is a risk of damaging the wafer during this process.

[0007] Also known is a method of forming a wax film by using a spin coating method (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 6-275503 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the method disclosed in Patent Document 1 has a problem that, although the film thickness is more uniform than the above-mentioned methods, the production cost increases because wax is wasted.

[0010] The present invention has been made in consideration of the above-mentioned facts, and its object is to provide a method for processing a workpiece that can reduce manufacturing costs while maintaining processing quality when thinning the workpiece. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems and achieve the object, the method for processing a workpiece of the present invention is a method for processing a workpiece, which is characterized by comprising: a preparation step of preparing a support substrate having at least one through hole and a sheet containing a thermoplastic resin; a fixing step of facing one side of the workpiece to the front side of the sheet and one side of the support substrate to the back side of the sheet, and heating the sheet to thermocompression-bond and fix the workpiece and the support substrate via the sheet; a processing step of holding the support substrate to which the workpiece is fixed on a holding table and processing the other side of the workpiece; a support substrate peeling step of supplying a fluid from the other side of the support substrate through the through hole to form a gap between the support substrate and the sheet, thereby peeling the support substrate from the sheet, after performing the processing step; and a sheet peeling step of peeling the sheet from the workpiece.

[0012] In the method for processing the workpiece, the fixing step may involve heating a sheet containing a thermoplastic resin while the sheet is further facing the other side of the support substrate, thereby fixing the sheet to the other side of the support substrate as well.

[0013] In the method for processing the workpiece, the through holes may be formed in multiple locations in the support substrate, and the density of the through holes formed in the peripheral region of the support substrate may be set to be higher than the density of the through holes formed in the central region of the support substrate. Effect of the Invention

[0014] The present invention has an effect of making it possible to reduce manufacturing costs while maintaining processing quality when thinning a workpiece. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view that illustrates an example of a workpiece to be processed by the workpiece processing method according to the first embodiment. [Diagram 2] FIG. 2 is a flowchart showing the flow of the workpiece processing method according to the first embodiment. [Diagram 3] FIG. 3 is a perspective view showing a support substrate, a sheet, etc., which are prepared in the preparation step of the method for processing the workpiece shown in FIG. [Figure 4] FIG. 4 is a plan view showing a first modification of the support substrate shown in FIG. [Diagram 5] FIG. 5 is a plan view showing a second modified example of the support substrate shown in FIG. [Figure 6] FIG. 6 is a plan view showing a third modification of the support substrate shown in FIG. [Figure 7] FIG. 7 is a plan view showing a fourth modified example of the support substrate shown in FIG. [Figure 8] FIG. 8 is a side view, partly in section, which is a schematic diagram showing the fixing step of the method for processing the workpiece shown in FIG. [Figure 9] FIG. 9 is a side view that illustrates a processing step of the method for processing the workpiece illustrated in FIG. [Figure 10] FIG. 10 is a side view that typically illustrates a state in which the second sheet is peeled off in the support substrate peeling step of the method for treating the workpiece illustrated in FIG. [Figure 11]FIG. 11 is a side view that typically illustrates a state in which the support substrate is peeled off from the sheet in the support substrate peeling step of the method for treating the workpiece shown in FIG. [Figure 12] FIG. 12 is a side view diagrammatically showing a sheet peeling step of the method for treating the workpiece shown in FIG. [Figure 13] FIG. 13 is a side view, partially in cross section, illustrating a support substrate peeling step in the method for processing a workpiece according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0017] [Embodiment 1] A method for processing a workpiece according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing a schematic diagram of an example of a workpiece to be processed by the method for processing a workpiece according to the first embodiment. Fig. 2 is a flow chart showing the flow of the method for processing a workpiece according to the first embodiment.

[0018] (workpiece) The method for processing a workpiece according to the first embodiment is a method for performing a grinding process on the workpiece 1 shown in Fig. 1 to thin the workpiece 1 to a predetermined finishing thickness 2. In the first embodiment, the workpiece 1 to be processed by the method for processing a workpiece according to the first embodiment is a wafer such as a disk-shaped semiconductor wafer having a substrate 3 made of SiC (silicon carbide), GaAs (gallium arsenide), or the like.

[0019] 1, the workpiece 1 has devices 6 formed in each of the regions defined by a plurality of planned division lines 5 on the surface 4. The devices 6 are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integrations), or various types of memories (semiconductor memory devices).

[0020] (Method of processing workpiece) The method for processing a workpiece according to the first embodiment is a method for performing a grinding process on the above-mentioned workpiece 1. The method for processing a workpiece according to the first embodiment includes a preparation step 101, a fixing step 102, a processing step 103, a support substrate peeling step 104, and a sheet peeling step 105, as shown in FIG.

[0021] (Preparation step) Fig. 3 is a perspective view showing a support substrate and a sheet, etc., prepared in a preparation step of the method for processing a workpiece shown in Fig. 2. Fig. 4 is a plan view showing a first modified example of the support substrate shown in Fig. 3. Fig. 5 is a plan view showing a second modified example of the support substrate shown in Fig. 3. Fig. 6 is a plan view showing a third modified example of the support substrate shown in Fig. 3. Fig. 7 is a plan view showing a fourth modified example of the support substrate shown in Fig. 3.

[0022] The preparation step 101 is a step of preparing a support substrate 10 having at least one through hole 11 and a sheet 20 containing a thermoplastic resin. In the first embodiment, in the preparation step 101, in addition to the workpiece 1 described above, the support substrate 10 and the sheet 20 are prepared as shown in FIG.

[0023] The support substrate 10 is made of a hard material with a constant thickness, and is a highly rigid substrate. In the first embodiment, the support substrate 10 is made of sapphire or the like, and is formed in a disk shape with a thickness greater than that of the workpiece 1 before grinding and the same diameter as the workpiece 1. In the first embodiment, the support substrate 10 has a plurality of through holes 11 penetrating in the thickness direction. In the first embodiment, the support substrate 10 has one through hole 11 in the center in a plan view, and a plurality (eight) of through holes 11 equally spaced in the circumferential direction on the outer edge.

[0024] In this manner, in the first embodiment, the density of through holes 11 formed in the outer edge portion, which is the peripheral region of the support substrate 10, is set to be higher than the density of through holes 11 formed in the center, which is the central region of the support substrate 10. The density of through holes 11 refers to the number of through holes 11 per unit area on both sides 12 and 13 of the support substrate 10.

[0025] However, in the present invention, as long as the support substrate 10 has at least one through hole 11, the number and arrangement of the through holes 11 are not limited to those of the first embodiment, as shown in Figs. 4, 5, 6 and 7. In the first modification shown in Fig. 4, the support substrate 10 has only one through hole 11 at the center. In the second modification shown in Fig. 5, the support substrate 10 has one through hole 11 at the center, and the through holes 11 are radially and equidistantly spaced from the center to the outer edge. In the third modification shown in Fig. 6, the support substrate 10 has one through hole 11 at the center, and the through holes 11 are equidistantly spaced in the circumferential direction at the outer edge. In the fourth modification shown in Fig. 7, the support substrate 10 has the through holes 11 equidistantly spaced in two directions perpendicular to each other. If the through hole 11 is too large, the shape of the through hole 11 may be transferred to the workpiece 1 during grinding, and if the through hole 11 is too small, the fluid 63 may not be properly supplied, and the support substrate 10 may not be peeled off properly. For this reason, in the present invention, it is desirable that the through hole 11 is of a size that allows the fluid 63 to be appropriately supplied and the support substrate 10 to be peeled off without the shape of the through hole 11 being transferred to the workpiece 1 during grinding processing.

[0026] The sheet 20 includes a thermoplastic resin and has flexibility. In the first embodiment, the thermoplastic resin constituting the sheet 20 is specifically an acrylic resin, a methacrylic resin, a vinyl resin, polyacetal, natural rubber, butyl rubber, isoprene rubber, chloroprene rubber, polyethylene, polypropylene, poly(4-methyl-1-pentene), poly(1-butene), and other polyolefins, polyesters, such as polyethylene terephthalate and polybutylene terephthalate, polyamides, such as nylon-6, nylon-66, and polymetaxylene adipamide, polyacrylates, polymethacrylates, polyvinyl chloride, polyetherimides, polyacrylonitrile, polyisobutylene ... Examples of the resin include one or more selected from nitrile, polycarbonate, polystyrene, polysulfone, polyethersulfone, polyphenylene, ether polybutadiene resin, polycarbonate resin, thermoplastic polyimide resin, thermoplastic polyurethane resin, phenoxy resin, polyamideimide resin, fluororesin, ethylene-unsaturated carboxylic acid copolymer resin, ethylene-vinyl acetate copolymer resin, ionomer, ethylene-vinyl acetate-maleic anhydride terpolymer resin, ethylene-vinyl acetate copolymer saponified resin, and ethylene-vinyl alcohol copolymer resin.

[0027] Examples of the unsaturated carboxylic acid constituting the ethylene-unsaturated carboxylic acid copolymer include acrylic acid, methacrylic acid, maleic acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, and itaconic anhydride. Here, the ethylene-unsaturated carboxylic acid copolymer includes not only a binary copolymer of ethylene and an unsaturated carboxylic acid, but also a multi-component copolymer in which other monomers are further copolymerized. Examples of the other monomers that may be copolymerized in the ethylene-unsaturated carboxylic acid copolymer include vinyl esters such as vinyl acetate and vinyl propionate, and unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, methyl methacrylate, isobutyl methacrylate, dimethyl maleate, and diethyl maleate.

[0028] In the first embodiment, the softening point of the sheet 20 is adjusted to 0° C. or more and 300° C. or less (preferably 80° C. or more and 100° C. or less) by appropriately adjusting the components, molecular weight, etc. of the thermoplastic resin described above. In the first embodiment, the storage modulus of the sheet 20 at 10° C. to 30° C. is 1×10 6 (Pa) or more and 1×10 9 (Pa) or less, and the storage modulus at temperatures of 80°C to 100°C when heated (applied) is 1×10 6 (Pa) or more and 1×10 7 (Pa) or less.

[0029] In the first embodiment, the sheet 20 has a thickness of 150 μm, and is formed in a disk shape that is the same shape as the workpiece 1 and the support substrate 10.

[0030] (fixed step) Fig. 8 is a side view, partially in cross section, that typically illustrates the fixing step of the method for processing the workpiece shown in Fig. 2. Fixing step 102 is a step in which one surface 4 of workpiece 1 faces one surface 21 of sheet 20, one surface 12 of support substrate 10 faces back surface 22 of sheet 20, and sheet 20 is heated to thermocompress and fix workpiece 1 and support substrate 10 via sheet 20.

[0031] In the first embodiment, in the fixing step 102, the front surface 4 of the workpiece 1 is faced to the front surface 21 of the sheet 20, and one surface 12 of the support substrate 10 is faced to the back surface 22 of the sheet 20. Furthermore, in the first embodiment, in the fixing step 102, as shown in Fig. 8, the front surface of a second sheet 30 having the same configuration as the sheet 20 is faced to the other surface 13 of the support substrate 10, the back surface of the second sheet 30 is placed on a flat holding surface 42 of a heating table 41 of a fixing device 40, and the second sheet 30, the support substrate 10, the sheet 20, and the workpiece 1 are sequentially placed on the holding surface 42.

[0032] In embodiment 1, in the fixing step 102, the flat pressing surface 44 of the pressing member 43 is placed on the other surface, that is, the back surface 7, of the workpiece 1, and a heater 45 built into the heating table 41 and a heater 46 built into the pressing member 43 are heated to a temperature above the softening point and below the melting point of the sheets 20, 30 while maintaining the distance between the holding surface 42 and the pressing surface 44 at a predetermined specified distance, and the pressing member 43 presses the workpiece 1, sheet 20, supporting substrate 10 and second sheet 30 toward the holding surface 42.

[0033] Then, the sheets 20 and 30 are heated by the heaters 45 and 46 to a temperature exceeding the softening point and below the melting point, and softened, the sheet 20 is bonded to the front surface 4 of the workpiece 1 and one surface 12 of the support substrate 10, and the second sheet 30 is bonded to the other surface 13 of the support substrate 10. The front surface 21 of the sheet 20 is thermocompression bonded to the front surface 4 of the workpiece 1, the back surface 22 of the sheet 20 is thermocompression bonded to the one surface 12 of the support substrate 10, and the second sheet 30 is thermocompression bonded to the other surface 13 of the support substrate 10, so that the workpiece 1, the sheet 20, the support substrate 10, and the second sheet 30 are integrated and fixed to each other. Thus, in the fixing step 102 in the first embodiment, the second sheet 30, which is a sheet containing a thermoplastic resin, is heated in a state in which the second sheet 30 is further faced to the other surface 13 of the support substrate 10, and the second sheet 30 is fixed to the other surface 13 of the support substrate 10 as well.

[0034] In the present invention, the second sheet 30 does not have to be provided. Also, in the present invention, it is sufficient if only one of the heaters 45, 46 is provided. Also, in the present invention, instead of the pressing member 43, a rolling roller that rolls on the back surface 7 of the workpiece 1 and presses the workpiece 1 etc. toward the holding surface 42 may be used. Also, in the present invention, the workpiece 1, the sheet 20, the support substrate 10 and the second sheet 30 may be inserted into a vacuum chamber and fixed to each other by drawing a vacuum between them, for example.

[0035] (Processing steps) Fig. 9 is a side view showing a schematic diagram of the processing steps of the method for processing the workpiece shown in Fig. 2. Processing step 103 is a step of holding support substrate 10, to which workpiece 1 is fixed, by holding table 51, and grinding back surface 7, which is the other surface of workpiece 1. In the first embodiment, in processing step 103, back surface 7 of workpiece 1 is ground.

[0036] In the first embodiment, in the processing step 103, the grinding device 50 sucks and holds the other surface 13 side of the support substrate 10 on the holding surface 52 of the holding table 51 via the second sheet 30. In the first embodiment, in the processing step 103, as shown in Fig. 9, the grinding device 50 rotates the grinding wheel 54 about its axis by the spindle 53 and rotates the holding table 51 about its axis, while supplying grinding fluid from a grinding fluid nozzle (not shown), and brings the grinding stone 55 of the grinding wheel 54 into contact with the back surface 7 of the workpiece 1 and approaches the holding table 51 at a predetermined feed rate, thereby grinding the back surface 7 of the workpiece 1 with the grinding stone 55.

[0037] In the first embodiment, in the processing step 103, the grinding device 50 grinds the back surface 7 of the workpiece 1 until the thickness of the workpiece 1 reaches the finish thickness 2. In the first embodiment, in the processing step 103, when the thickness of the workpiece 1 reaches the finish thickness 2, the grinding device 50 moves the grinding wheel 54 away from the back surface 7 of the workpiece 1.

[0038] (Support substrate peeling step) Fig. 10 is a side view showing a state in which the second sheet is peeled off in the support substrate peeling step of the method for treating the workpiece shown in Fig. 2. Fig. 11 is a side view showing a state in which the support substrate is peeled off from the sheet in the support substrate peeling step of the method for treating the workpiece shown in Fig. 2.

[0039] In the support substrate peeling step 104, after the processing step 103 is performed, a fluid 63 is supplied from the other surface 13 of the support substrate 10 through the through hole 11 to form a gap between the support substrate 10 and the sheet 20, thereby peeling the support substrate 10 from the sheet 20. In the first embodiment, in the support substrate peeling step 104, the back surface 7 of the workpiece 1 is sucked and held on the flat suction surface 62 of the suction unit 61 of the peeling device 60, and the workpiece 1, sheet 20, support substrate 10 and second sheet 30, which are integrated with each other, are lifted from the holding surface 52 of the holding table 51.

[0040] In the first embodiment, in the support substrate peeling step 104, as shown in FIG. 10, the second sheet 30 is peeled from the other surface 13 of the support substrate 10 in order from the end. Then, the through hole 11 opens on the other surface 13 side of the support substrate 10. In the first embodiment, in the support substrate peeling step 104, as shown in FIG. 11, the peeling device 60 supplies a fluid 63 containing at least one of water and air into the through hole 11 from the opening on the other surface 13 side of the through hole 11. Then, a gap is generated between the back surface 22 of the sheet 20 and the support substrate 10. Thereafter, in the support substrate peeling step 104, the support substrate 10 is peeled off from the sheet 20.

[0041] In the present invention, in the support substrate peeling step 104, the workpiece 1, sheet 20, support substrate 10 and second sheet 30 which have been integrated with each other after the processing step 103 may be turned upside down, the back surface 7 of the workpiece 1 may be held by a holding unit, and the second sheet 30 may be peeled off from above and the fluid 63 may be supplied. In the present invention, in the support substrate peeling step 104, if the support substrate 10 is not peeled off only by supplying the fluid 63, the support substrate 10 may be peeled off by suction holding and separating it.

[0042] (Sheet peeling step) Fig. 12 is a side view that typically shows a sheet peeling step of the method for processing the workpiece shown in Fig. 2. The sheet peeling step 105 is a step of peeling the sheet 20 from the workpiece 1. In the first embodiment, as shown in Fig. 12, in the sheet peeling step 105, the sheet 20 is peeled off from the front surface 4 of the workpiece 1 in order from the edge while the back surface 7 of the workpiece 1 is held by suction on the flat suction surface 62 of the suction unit 61 of the peeling device 60.

[0043] In the method for processing a workpiece according to the first embodiment described above, the support substrate 10 having the through holes 11 formed therein and the workpiece 1 are fixed via the sheet 20 containing a thermoplastic resin, and then the processing step 103 is carried out. In this manner, in the method for processing a workpiece according to the first embodiment, the sheet 20 is fixed to the support substrate 10 and the workpiece 1 by thermocompression bonding, so that it is possible to fix them with high precision regardless of the skill level of the worker, and no wax is wasted.

[0044] Furthermore, in the method for processing a workpiece according to the first embodiment, after the processing step 103, while the workpiece 1 is held by suction, a fluid 63 is supplied from the through-hole 11 formed in the support substrate 10 to form a gap between the support substrate 10 and the sheet 20, and the support substrate 10 is peeled off from the sheet 20. For this reason, the method for processing a workpiece according to the first embodiment can prevent the workpiece 1 from bending when peeling off the sheet 20 from the workpiece 1, can prevent damage to the workpiece 1, and can easily peel off the support substrate 10, thereby improving productivity.

[0045] As a result, the method for processing a workpiece according to the first embodiment has the effect of making it possible to reduce the manufacturing cost while maintaining the processing quality when thinning the workpiece 1.

[0046] [Embodiment 2] A method for processing a workpiece according to embodiment 2 will be described with reference to the drawings. Fig. 13 is a side view, partially in cross section, showing a support substrate peeling step of the method for processing a workpiece according to embodiment 2. In Fig. 13, the same parts as those in embodiment 1 are denoted by the same reference numerals, and the description thereof will be omitted.

[0047] The processing method of the workpiece according to the second embodiment is the same as that of the first embodiment, except that the support substrate peeling step 104 is different. In the second embodiment, in the support substrate peeling step 104, as shown in FIG. 13, the other surface 13 of the support substrate 10 is placed on a flat holding surface 71 of a holding table 70 made of a porous material such as porous ceramic. In the second embodiment, in the support substrate peeling step 104, a fluid 63 is supplied to the holding surface 71 through a flow path 73 provided in a base 72 of the holding table 70, and the fluid 63 is supplied from the holding surface 71 to the through-holes 11 to form a gap between the sheet 20 and the support substrate 10. Thereafter, in the second embodiment, in the support substrate peeling step 104, the support substrate 10 is peeled off from the sheet 20.

[0048] In the method for processing a workpiece according to the second embodiment, a support substrate 10 having a through hole 11 formed therein and the workpiece 1 are fixed via a sheet 20 containing a thermoplastic resin, and then a processing step 103 is performed, and then a fluid 63 is supplied from the through hole 11 formed in the support substrate 10 to form a gap between the support substrate 10 and the sheet 20, and the support substrate 10 is peeled off from the sheet 20. As a result, the method for processing a workpiece according to the second embodiment, like the first embodiment, has the effect of making it possible to reduce manufacturing costs while maintaining processing quality when thinning the workpiece 1.

[0049] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. [Explanation of symbols]

[0050] 1 Workpiece 4. Surface (one side) 7 Back side (other side) 10 Support substrate 11 Through hole 12 One Side 13 The other side 20 sheets 21 Surface 22 Back side 30 2nd sheet (sheet) 51 Holding table 63 Fluid 101 Preparation Steps 102 fixed steps 103 Processing Steps 104 Support substrate peeling step 105 Sheet peeling step

Claims

1. A method for treating a workpiece, comprising the steps of: A preparation step of preparing a support substrate having at least one through hole and a sheet including a thermoplastic resin; a fixing step of placing one side of the workpiece on the front side of the sheet and one side of the support substrate on the back side of the sheet, and heating the sheet to thermocompress and fix the workpiece and the support substrate via the sheet; a processing step of holding the support substrate to which the workpiece is fixed by a holding table and processing the other surface of the workpiece; a support substrate peeling step in which, after the processing step is performed, a fluid is supplied from the other surface of the support substrate through the through hole to form a gap between the support substrate and the sheet, thereby peeling the support substrate from the sheet; a sheet peeling step of peeling the sheet from the workpiece; A method for processing a workpiece, comprising:

2. The method for processing a workpiece described in claim 1, characterized in that in the fixing step, the sheet containing a thermoplastic resin is heated while being further faced to the other side of the support substrate, thereby fixing the sheet to the other side of the support substrate as well.

3. A plurality of the through holes are formed in the support substrate, 3. A method for processing a workpiece as claimed in claim 1 or claim 2, characterized in that the density of the through holes formed in the peripheral region of the support substrate is set to be higher than the density of the through holes formed in the central region of the support substrate.

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